Chemistry
Give a reason for the following :
(a) Silver nitrate solution is kept in coloured bottles.
(b) Molybdenum is used in the manufacture of ammonia.
(c) A blue solution of copper sulphate changes to green when a piece of iron is added to this solution.
(d) Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.
Chemical Reaction
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Answer
(a) Silver nitrate solution is kept in brown bottles in the laboratory because it decomposes in the presence of light. It becomes black and forms silver, nitrogen dioxide and oxygen.
2AgNO3 2Ag + 2NO2 ↑ + O2 ↑
(b) Molybdenum acts as a promoter and increases the efficiency of the catalyst iron, hence it is used in the manufacture of ammonia.
(c) When a piece of iron is added to a blue coloured copper sulphate solution, the blue colour of the solution fades and eventually turns into light green due to the formation of ferrous sulphate.
(d) When a small piece of copper is added to concentrated sulphuric acid, a blue solution of copper sulphate is formed.
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Related Questions
Give an example of each of the following chemical changes.
(a) A photochemical reaction involving 1. silver salt 2. water
(b) A reaction involving 1. blue solution 2. formation of a dirty green precipitate
(c) Two gases combine to form a white solid.
(d) Two solids combine to form a liquid.
(e) A reaction where color change is noticed.
Write the chemical reaction where the following changes are observed.
(a) Gas is evolved
(b) Colour change is noticed
(c) Precipitate is formed
(d) Physical state of reactants is changed
Which of the following is not a characteristic of a chemical change?
(i) It is irreversible
(ii) No net energy change is involved
(iii) New substance is formed
(iv) Involves absorption or liberation of energy
A reaction of a type: AB + CD ⟶ AD + CB, involves
(i) no chemical change
(ii) decomposition of AB and CD
(iii) exchange of ions of AB and CD
(iv) combination of AB and CD